1. Field of the Invention
This invention relates generally to intravascular dilatation devices, and more specifically to intravascular devices to provide blood flow during dilatation and other therapeutic and diagnostic procedures.
In percutaneous transluminal angioplasty procedures, a catheter having an expansible distal end, usually in the form of a balloon, is positioned in a lumen of a blood vessel with the distal end disposed within a stenotic atherosclerotic region of the vessel. The expansible end is then expanded to dilate the vessel and restore adequate blood flow through the diseased region. During dilation blood flow is interrupted, limiting inflation time to between 0.5 and 3 minutes.
While angioplasty has gained wide acceptance, it continues to be limited by two major problems, abrupt closure and restenosis. Abrupt closure refers to the acute occlusion of a vessel immediately after or within the initial hours following the dilation procedure. This complication, occurring in approximately one in twenty cases, frequently results in myocardial infarction and death if blood flow is not quickly restored. At present, arterial dissections, one of the causes of abrupt closure, are treated by prolonged balloon inflations lasting more than 5 minutes. Special angioplasty balloon catheters which allow for perfusion through the dilation catheter during inflation are required for this purpose.
Restenosis refers to the re-narrowing of an artery after an initially successful angioplasty. Restenosis usually occurs within the initial six months after angioplasty and afflicts approximately one in three cases. Therefore, approximately one-third of treated patients will require additional revascularization procedures. Many different strategies have been tried unsuccessfully to reduce the restenosis rate, including mechanical (e.g., prolonged balloon inflations, atherectomy, laser and stenting) and pharmacologic (e.g., calcium antagonists, ace inhibitors, fish oils, steroids and anti-metabolic) approaches. One promising new strategy is to delivery agent directly to the arterial wall at the site of angioplasty. Several devices have been developed to deliver agent locally into the arterial wall. Similar to angioplasty balloon catheters, balloon deployed drug delivery catheters interrupt blood flow, limiting the time available to deliver agent.
Thus, it would be desirable to provide perfusion and agent delivery capabilities to angioplasty catheters for the treatment of abrupt closure and restenosis and for other purposes.
2. Description of the Background Art
A sleeve catheter intended for drug delivery when placed over an angioplasty balloon is described in U.S. Pat. No. 5,364,356. A drug delivery catheter having an internal blood perfusion lumen and external drug delivery balloon is described in WO93/21985. U.S. Pat. Nos. 5,318,535; 5,308,356; 5,300,085; 5,284,473; 5,087,247; 4,892,519; and 4,790,315, describe angioplasty balloon catheters having integral blood perfusion capability. U.S. Pat. No. 4,661,094, describes a blood perfusion catheter intended primarily to provide blood flow through an occluded blood vessel. U.S. Pat. Nos. 5,163,921 and 5,180,364, describe guiding catheters having perfusion flow ports at their distal ends. Angioplasty catheters having integral blood perfusion capability are commercially available, e.g., under the tradename ACS Rx Perfusion.TM. Coronary Dilatation Catheter, from Advanced Cardiovascular Systems, Inc., Temecula, Calif., as described in a package insert copyright 1990. A balloon angioplasty catheter having a tapered mandrel removably received in an inflation lumen therein for enhancing column strength is disclosed in U.S. Pat. No. 5,242,396. A balloon catheter having perfusion conduits formed in the balloon itself is described in U.S. Pat. No. 5,000,734.